Diverse match plate molding machines are conventionally used for producing flaskless sand molds. One typical example of the match plate molding machine is disclosed in Japanese Laid-Open Patent Application No. 54(1979)-110126. This match plate molding machine is provided with a match plate carrying thereon patterns, at least a pair of molding flasks for an upper and a lower sand mold, a pair of squeezing devices for compacting molding sand, and diverse means for removing upper and lower flaskless sand molds from the molding flasks. The pair of molding flasks is alternately positioned in a first mold-forming station in which a match plate is vertically held between the pair of squeezing devices movable toward and away from one another along a horizontal axis, and in a second mold-removing station in which a mold-jointing operation and a mold-removing operation are carried out by the cooperation of the diverse removing means. When the pair of molding flasks are positioned in the first mold-forming station, a mold-forming operation including filling of molding sands into the molding flasks, squeezing or compacting of the filled molding sands, and parting of the squeezed molding sands from the patterns of the match plate, is carried out by cooperation of the match plate, the molding flasks and the squeezing devices. However, during the mold-forming operation, difficulties such as breaking of the match plate and collapsing of sand molds sometimes occur. Therefore, in order to obviate the problems encountered with the conventional match plate molding machine, it is desired to provide an appropriate means for improving the mold-forming operation of the conventional match plate molding machine, for the purpose of eventually producing flaskless sand molds of a high quality.